Yes, I have always been fairly lean - which makes for good endurance cycling, but can be a little embarrassing when hanging around a the public pool; it seems like every other fit male these days sports well-defined pecs and a six-pack, but I've pretty much conceded this to them given my impending half- century mark.
i eat very well, lots of protein and complex fiber veggies and fruits, and I maintain a pretty consistent weight.
I think most vitamin supplements get pissed away, so I try to get most of them from food and fruit juices.
I lift a minimum of three times a week, starting with lower weights, and working to higher ones, to the point of exhaustion... I have seen a small increase in weight and endurance there, but it seems to be very slow going.
i could do a hundred push-ups easily 20-odd years ago, but did not pay much attention to core fitness in the ensuing years, and could barely do 25 when I got back into cycling and fitness a year ago. I have worked back up to 40-45, but seem to be stuck there for the past six months, no matter how consistently I work at it.
I was able to get my cycling fitness back up after about three months of training- going from barely-eight miles to over thirty in at time period (I have done a couple of fifties this year). But the upper body strength improvement seems to have stalled out.